Mazda 323F 1997 1.5 16v Z5 eng. code, have cured high emissions fault but reason why please.Archived Message
Posted by Martin Kelly on August 30, 2007, 11:05 pm
Had the above car in today for pre MOT check so did emission test. Passed fast idle easily but failed normal idle with 2.5% CO, 325 HC, 0.9 lambda approx. When I gave it light throttle the revs surged as though it was very lean. Scoped O2 sensor, stuck at 0.9v normal idle and switched fine at fast idle. Heater volts and resistance ok. Checked for vacuum leaks and found nothing, EGR all okay. Scoped TPS okay but when I adjusted it slightly the 02 sensor suddenly started switching and the emissions dropped to a pass and no more surging.
Now, I'm pleased it's fixed but I'm not exactly sure why and would really like to know.
Sorry I've gone on a bit but any pointers would be appreciated. Thanks, Martin.